Chahar (Mongolian: ᠴᠠᠬᠠᠷ/ Чахар; Chinese: 察哈爾; pinyin: Cháhā'ěr), also known as Chaha'er, Chakhar or Qahar, was a province of the Republic of China in existence from 1912 to 1936, mostly covering territory in what is part of Eastern Inner Mongolia. It was named after the Chahar Mongols.

Chahar Province is named after the Chahar, a tribal group of the Mongols who live in that area. The area was controlled (in part or fully) by various empires that ruled over China's north including the Han, Tang, Liao, and Jin dynasties. After the unification of the Mongol tribes under Genghis Khan, the area came under Yuan rule. After the Yuan dynasty (1271–1368), the area was a battleground between the Ming dynasty and Northern Yuan. Then the Chahar tribe became the personal appanage of the monarchs of the Northern Yuan dynasty since the reign of Batumongke Dayan Khan (r. 1479–1517). By the Qing dynasty (1644–1912), Chahar was a "Zhangyuan Special Region" (張垣特區), although Yao Xiguang (姚錫光) proposed making Chahar a province as early as 1908.

In 1913, the second year of the Republic of China, Chahar Special Administrative Region was created as a subdivision of Zhili Province, containing 6 Banners and 11 counties:

Zhāngbèi (張北) Duōlún (多倫) Gǔyuán (沽源) Shāngdū (商都)

Bǎochāng (寶昌) Kāngbǎo (康保) Xīnghé (興和) Táolín (陶林)

Jíníng (集寧) Fēngzhèn (豐鎮) Liángchéng (涼城)

In 1928, it became a province. The last five counties on the above list (starting from Xinghe) were partitioned to Suiyuan province. And ten counties were included from Xuanhua Subprefecture (宣化府), Koubei Circuit (口北道), Hebei Province:

Xuānhuà (宣化) Chìchéng (赤城) Wànquán (萬全) Huáilái (懷來)

Yù (蔚) Yángyuán (陽原) Lóngguān (龍關) Yánqìng (延慶)

Huái'ān (懷安) Zhuōlù (涿鹿)

All banners belong to the Shilingol League (ᠰᠢᠯᠢ ᠶᠢᠨᠭᠣᠤᠯ, 锡林郭勒盟).

From 1937 to 1945, it was occupied by Japan and made a part of Mengjiang, a Japanese-controlled region led by Mongol Prince Demchugdongrub of the Shilingol Alliance. The Chahar People's Anti-Japanese Army Alliance (察哈爾民眾抗日同盟軍) was established in Kalgan on May 26, 1933 by Feng Yuxiang (馮玉祥) and Ji Hongchang (吉鴻昌).

In 1952, six years after becoming communist, the province was abolished and divided into parts of Inner Mongolia, Beijing Municipality and Hebei.

Name	Administrative Seat	Simplified Chinese	Hanyu Pinyin	Subdivisions
Zhangjiakou	Zhangjiakou	张家口市	Zhāngjiākǒu Shì	none
Datong	Datong	大同市	Dàtóng Shì	none
Yanbei Division	Datong County	雁北专区	Yànběi Zhuānqū	13 counties
Qanan Division	Xuanhua County	察南专区	Chánán Zhuānqū	11 counties
Qabei Division	Zhangbei County	察北专区	Cháběi Zhuānqū	9 counties

Chahar Province was divided north-south by the Great Wall, with North Chahar being the larger in area and South Chahar, with the capital, Zhangjiakou, being far larger in population. It had an area of 278.957 km (107.706 sq mi). In North Chahar most of the land was part of the northeastern extension of the Gobi Desert.

• North: Xing'an
• North and West: Mongolia
• West and South : Suiyuan
• South: Shanxi and Hebei
• East: Rehe and Liaobei

• Inner Mongolia § Republic of China and the Second World War periods

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